1. Technical Field of the Invention
Implementations consistent with the principles of the invention generally relate to the field of display devices, more specifically to latency control in display devices.
2. Background of Related Art
Video display technology may be conceptually divided into analog-type display devices (such as cathode ray tubes (“CRTs”)) and digital-type display devices (such as liquid crystal displays (“LCDs”), plasma display panels, and the like), each of which must be driven by appropriate input signals to successfully display an image. For example, a typical analog system may include an analog source (such as a personal computer (“PC”), digital video disk (“DVD”) player, and the like) coupled to a display device (sometimes referred to as a video sink) by way of a communication link. The communication link typically takes the form of a cable (such as an analog video graphics array (“VGA”) cable in the case of a PC) well known to those of skill in the art.
More recently, digital display interfaces have been introduced, which typically use digital-capable cables. For example, the Digital Visual Interface (“DVI”) is a digital interface standard created by the Digital Display Working Group (“DDWG”), and is designed for carrying digital video data to a display device. According to this interface standard, data are transmitted using the transition-minimized differential signaling (“TMDS”) protocol, providing a digital signal from a PC's graphics subsystem to the display device, for example. As another example, DisplayPort™ is a digital video interface standard from the Video Electronics Standards Association (“VESA”). DisplayPort™ may serve as an interface for CRT monitors, flat panel displays, televisions, projection screens, home entertainment receivers, and video port interfaces in general. In one embodiment, DisplayPort™ provides four lanes of data traffic for a total bandwidth of up to 10.8 gigabits per second, and a separate bi-directional channel handles device control instructions. DisplayPort™ embodiments incorporate a main link, which is a high-bandwidth, low-latency, unidirectional connection supporting isochronous stream transport. Each DisplayPort™ main link may comprise one, two, or four double-terminated differential-signal pairs with no dedicated clock signal; instead, the data stream is encoded using 8B/10B signaling, with embedded clock signals. AC coupling enables DisplayPort™ transmitters and receivers to operate on different common-mode voltages. In addition to digital video, DisplayPort™ interfaces may also transmit audio data, eliminating the need for separate audio cables.
As display devices strive to improve image quality by providing various stages of image processing, they may introduce longer and longer delays between the time that image data enters the display device and the time that it is finally displayed. Such a delay, sometimes called “display latency,” may create unacceptable time differences in the system (e.g., between the source device and the display device), and may also degrade its usability from a user control point of view. For example, if the source device is a game console, a long delay between the time that an image enters the display device and the time that it is actually displayed may render the game unplayable. For instance, consider a game scenario in which a character must jump over an obstacle. As the scenario progresses, the user naturally perceives and determines the proper time to jump based upon the physically displayed image. If the time lag between the time that the image enters the display device and the time that it is shown is too long, the game character may have already crashed into the object before the user activates the “jump” button.
As another example, this problem may also be experienced in situations where a user transmits commands to a source device, such as by activating buttons on a remote control device or directly on the source device console. If the delay from the time that image data enters the display device to the time that it is actually displayed is too long, the user may become frustrated by the time lag experienced between the time that a command was issued (e.g., the time that the user pressed a button on the source device or its remote control) to the time that execution of the command is perceived or other visual feedback is provided by the system (e.g., the time that the user sees a response on the display device).
It is desirable to address the limitations in the art.